All newer kernels than the 1.5.2 GENERIC have the same problem on my SS2.
Although I have "pseudo-device   ipfilter" and "IPFILTER_LOG" in my kernel 
config, ipfilter doesn't work with this kernel.(the Kernel-Field in 'ipf -V  
' is blank and there are errors when adding filter rules). This happens with 
GENERIC-compiled kernels, too. It's just like ipfilter wasn't compiled in.

Is there a general issue with ipfilter on a sun4c?
Strange is also, that the redirection in my current kernel(1.5.2 Gen.) 
doesn't work at all.
Sample Setting(gnutella-port)
rdr ppp0 0/0 port 6346 -> 192.168.0.3 port 6346 tcp

Manuel Heinzmann